In the Baker, et al. U.S. Pat. No. 3,499,167, issued Mar. 3, 1970, there is disclosed a multiple discharge display and/or memory panel which may be characterized as being of the pulsing discharge type having a gaseous medium, usually a mixture of two gases at a relatively high gas pressure, in a thin gas chamber or space between opposed dielectric charge storage members which are backed by conductor arrays. The conductor arrays backing each dielectric member are transversely oriented to define or locate a plurality of discrete discharge volumes or sites and constitute a discrete discharge unit. In some cases, the discharge units may be additionally defined by physical structures such as perforated glass plates and the like and in other cases capillary tubes and like structures may be used. In the above-identified patent application of Baker, et al., physical barriers and isolation members for discrete discharge sites have been eliminated. In such devices charges (electrons and ions) produced upon ionization of the gas at a selected discharge site or conductor crosspoint, when proper operating potentials are applied to selected conductors thereof, are stored upon the surfaces of the dielectric at the selected locations or sites and constitute an electrical field opposing the electrical field which created them. After a firing potential has been applied to initiate a discharge, the electrical field created by the charges stored upon the dielectric members aids in initiating subsequent momentary or pulsing discharges on succeeding half cycles of an applied sustaining potential so that the applied potential, and hence the storage charges indicate the previous discharge condition of a discharge unit or site and can constitute an electrical memory.
In dynamic operation, in addition to the sustaining voltages, writing and erasing pulses may be superimposed on and algebraically added to the sustaining wave forms applied to selected transverse conductor pairs in the conductor arrays to manipulate discharge conditions of discharge sites. Some of the preferred types of circuits for supplying the sustaining potentials, and for generating the manipulating pulses to be added to the sustaining potentials, utilize output transistors which are driven into deep saturation to abruptly switch the wave form from one potential level to another. Difficulties have been encountered in the past, in that when a transistor is turned "on" and driven into deep saturation, it is difficult to bring the transistor out of saturation and turn it "off" quickly. This makes control of the shape of the trailing edge of the wave form difficult, may interfere with the addition of manipulating pulses, etc. and is undesirable. Diode clamping circuits have been proposed and are useful in certain applications for bringing the transistor out of saturation within the time limits of those systems. However, as the switching speeds increase and as the type of wave forms applied as sustaining potentials and as manipulating pulses become more complex, the diode clamping circuit is not suitable for all applications.
Accordingly, it is an object of this invention to provide an improved system for supplying operating potentials to load devices, particularly wherein the load devices are of the gas discharge display/memory type.
It is another object of this invention to provide improved voltage wave form generating means which includes at least two sections, each of the sections having an output transistor to connect first and second potential levels to the load device. The turn "on" and turn "off" of the output transistors is coordinated so that a turn-off signal for one section will overlap in time a turn-on signal for the other section, to prevent current spiking of the output transistor means being turned "off".
It is a further object of this invention to provide improved control apparatus for transistors in which novel transformer-diode clamping circuits may be utilized to bring the transistor out of saturation and permit the transistor to be turned "off" more quickly. In addition, novel means are shown for driving the transistors into saturation more quickly.